This invention relates to a tubular article and specifically to a vascular graft containing an absorbable or absorbable/nonabsorbable biomaterial. The use of the vascular graft is for repair of the peripheral vascular system and for coronary bypass.
The absorbable material fosters increased tissue ingrowth into the graft as compared to nonabsorbable grafts. Increased tissue ingrowth leads to greater patency through formation of a vascularized neointima and less tendency to be aneurysmal through formation of a suitable adventitia.
The absorbable material can vary and includes polyglycolic acid (hereafter PGA), and a copolymer comprising glycolic acid ester and trimethylene carbonate linkages, e.g. the copolymer in the MAXON.TM. (American Cyanamid Company, Wayne, N.J. 07470 U.S.A.) suture.
The nonabsorbable material (which is used as the backbone) can be proprietary materials, e.g. a Hytrel.TM. (E. I. du Pont and Co., Wilmington, Del., U.S.A.) polymer, such as the polymer in the NOVAFIL.TM. (American Cyanamid Company, Wayne N.J.) suture. Alternatively, the nonabsorbable material can be more conventional polymers including a polyester, polyamide or polypropylene.
There has been a long felt need in the vascular graft art to develop a small diameter graft which will be generally acceptable to essentially all of the surgical community. The reasons for this long felt need are many and relate both to the biological requirements for a small diameter graft and to the limitations of the biomaterials generally used for these applications. Consequently, prior art small diameter vascular grafts, e.g. at or less than 8 mm diameter to even smaller diameter grafts, e.g. at or less than 4 mm diameter, have not been universally accepted by the surgical community.
Various prior art vascular graft constructions and/or biomaterials have been used in an attempt to solve this long felt need. These prior art solutions have included but are not limited to, one or a combination of the following parameters:
1. Knitted or woven textile structures as vascular grafts for coronary artery bypass and the peripheral vascular system. PA0 2. a. Vascular grafts having a biocomponent structure, i.e. one or more absorbable and nonabsorbable materials. PA0 3. PGA as the absorbable component. PA0 4. A polyester, e.g. Dacron.TM. (E. I. DuPont & Co., Del., U.S.A.), a polyamide, or a polypropylene as the nonabsorbable component. PA0 a. What is the porosity of the vascular graft? PA0 b. What is the compliance of the vascular graft? PA0 c. What are the optimum textile and biological factors for manufacturing a graft, having a double tube configuration specifically, a nonabsorbable outer tube and an absorbable inner tube structure? PA0 d. What are the optimum textile and biological factors for manufacturing a vascular graft having an external support structure? PA0 (1) Dacron.TM. is known from the prior art to incite a thrombogenic reaction. PA0 (2) Dacron.TM. or Novafil.TM. fibers can be shielded from blood by inner layers of PGA and MAXON.TM., thereby minimizing the tendency to thrombose and occlude the graft. PA0 (3) As PGA and then MAXON.TM. degrade and are absorbed, the inner capsule becomes larger and, hence, has a higher probability of remaining patent in small diameter applications. PA0 (4) Based upon animal studies, a PGA- and MAXON.TM.-containing graft tends to have greater patency than a commercial graft material.
b. The percentage of the absorbable material has varied from about 25 to less than 100%.
None of these prior art solutions have been universally accepted by the surgical community for a small diameter vascular graft. Therefore, the surgical community continues to feel the need for an absorbable or absorbable/nonabsorbable small diameter vascular graft having a diameter of 8 mm, or less, and more specifically 4 mm, or less.
To solve this long felt need, critical questions about vascular graft construction and use have to be considered, including, but not limited to, the following: